/*
Request/Reply (I ask, you answer)
I ask
Request/Reply is used for synchronous communications where each question is responded with a single answer, for example remote procedure calls (RPCs). 
Like Pipeline, it also can perform load-balancing. This is the only reliaable messaging pattern in the suite, 
as it automatically will retry if a request is not matched with a response.

Blithely assumes message is ASCIIZ string. Real code should check it.
Compilation
gcc reqrep.c -lnanomsg -o reqrep
Execution
./reqrep node0 ipc:///tmp/reqrep.ipc & node0=$! && sleep 1
./reqrep node1 ipc:///tmp/reqrep.ipc
kill $node0
Output
NODE1: SENDING DATE REQUEST DATE
NODE0: RECEIVED DATE REQUEST
NODE0: SENDING DATE Sat Sep  7 17:39:01 2013
NODE1: RECEIVED DATE Sat Sep  7 17:39:01 2013
*/



#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <nanomsg/nn.h>
#include <nanomsg/reqrep.h>

#define NODE0 "node0"
#define NODE1 "node1"
#define DATE "DATE"

#pragma comment(lib, "nanomsg.lib")

void
fatal(const char *func)
{
	fprintf(stderr, "%s: %s\n", func, nn_strerror(nn_errno()));
	exit(1);
}

char *
date(void)
{
	time_t now = time(&now);
	struct tm *info = localtime(&now);
	char *text = asctime(info);
	text[strlen(text) - 1] = '\0'; // remove '\n'
	return (text);
}

int
node0(const char *url)
{
	int sz_date = strlen(DATE) + 1; // '\0' too
	int sock;
	int rv;

	if ((sock = nn_socket(AF_SP, NN_REP)) < 0) {
		fatal("nn_socket");
	}
	if ((rv = nn_bind(sock, url)) < 0) {
		fatal("nn_bind");
	}
	for (;;) {
		char *buf = NULL;
		int bytes;
		if ((bytes = nn_recv(sock, &buf, NN_MSG, 0)) < 0) {
			fatal("nn_recv");
		}
		if ((bytes == (strlen(DATE) + 1)) && (strcmp(DATE, buf) == 0)) {
			printf("NODE0: RECEIVED DATE REQUEST\n");
			char *d = date();
			int sz_d = strlen(d) + 1; // '\0' too
			printf("NODE0: SENDING DATE %s\n", d);
			if ((bytes = nn_send(sock, d, sz_d, 0)) < 0) {
				fatal("nn_send");
			}
		}
		nn_freemsg(buf);
	}
}

int
node1(const char *url)
{
	int sz_date = strlen(DATE) + 1; // '\0' too
	char *buf = NULL;
	int bytes = -1;
	int sock;
	int rv;

	if ((sock = nn_socket(AF_SP, NN_REQ)) < 0) {
		fatal("nn_socket");
	}
	if ((rv = nn_connect(sock, url)) < 0) {
		fatal("nn_connect");
	}
	printf("NODE1: SENDING DATE REQUEST %s\n", DATE);
	if ((bytes = nn_send(sock, DATE, sz_date, 0)) < 0) {
		fatal("nn_send");
	}
	if ((bytes = nn_recv(sock, &buf, NN_MSG, 0)) < 0) {
		fatal("nn_recv");
	}
	printf("NODE1: RECEIVED DATE %s\n", buf);
	nn_freemsg(buf);
	return (nn_shutdown(sock, 0));
}

int
main(const int argc, const char **argv)
{
	if ((argc > 1) && (strcmp(NODE0, argv[1]) == 0))
		return (node0(argv[2]));

	if ((argc > 1) && (strcmp(NODE1, argv[1]) == 0))
		return (node1(argv[2]));

	fprintf(stderr, "Usage: reqrep %s|%s <URL> ...\n", NODE0, NODE1);
	return (1);
}